Alkene isomerization as an entry to efficient alternating ring-opening metathesis polymerization (i-AROMP)

ABSTRACT

This invention relates to the field of polymers and olefin polymerization, and more specifically olefin metathesis polymerization. Specifically, the present invention provides a polymer comprising rigorously alternating AB subunits and methods of formation of the AB alternating polymers. In the polymers and process of the invention, the A monomer is derived from a cyclobutene derivative, and the B monomer is derived from a cyclohexene derivative. The polymerization takes place in the presence of an olefin metathesis catalyst.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 of PCT/US2016/023457 which claims the benefit of priority to U.S. Application No. 62/136,436, filed Mar. 20, 2015, each of which is incorporated herein by reference in its entirety.

STATEMENT OF GOVERNMENT INTEREST

This invention was made with government support under GM097971, GM074776, and HD038519 awarded by the National Institutes of Health. The government has certain rights in the invention.

FIELD OF THE INVENTION

This invention relates to the field of polymers and olefin polymerization, and more specifically olefin metathesis polymerization. Specifically, the present invention provides a polymer comprising rigorously alternating AB subunits and methods of formation of the AB alternating polymers.

BACKGROUND

Copolymers are employed in a wide range of materials, ranging from bulk plastics to specialized coatings, pharmaceutical compositions, and biomedical and electronic devices. Among the most commonly used are block copolymers, which often rely on phase separation of the two blocks for their functional properties, for example in drug delivery nanoparticles, and random copolymers, which incorporate two or more functional moieties that act co-operatively, for example in organic light emitting diodes. Regularly alternating polymers allow for controlled positioning of functional substituents, but they are difficult to access synthetically.

Regioregular alternating polymers (for example, SAN, styrene-acrylonitrile, an alternating copolymer used in plastics) are generally synthesized by radical polymerization with kinetic control of alternation in the polymerization reaction. (Hawker, C. J.; Bosman, A. W.; Harth, E. Chemical Reviews 2001, 101, 3661-3688; Matyjaszewski, K.; Xia, J. H. Chemical Reviews 2001, 101, 2921-2990). Recently, ring opening metathesis polymerization (ROMP) and ring opening insertion metathesis polymerization (ROIMP) have been employed to synthesize alternating polymers: Ilker, M. F.; Coughlin, E. B. Macromolecules 2002, 35, 54-58; Choi, T. L.; Rutenberg, I. M.; Grubbs, R. H. Angewandte Chemie-Intl. Ed. 2002, 41, 3839-3841; PCT publication WO 03/070779.

The existing methods of formation of alternating polymers are limited, and there remains a need for new and more structurally diverse substrates and polymers. The present invention provides substrate and catalyst combinations that can generate a wider range of alternating polymers, having a range of diverse properties.

BRIEF DESCRIPTION OF THE INVENTION

The invention provides an AB copolymer and a method for producing an alternating AB copolymer comprising the repeating unit I,

in which the A monomer is derived from a cyclobutene derivative III or III′, and the B monomer is derived from a cyclohexene derivative II.

In embodiments starting from cyclobutene III, in a first step the cyclobutene III is isomerized to III′ in the presence of an olefin metathesis catalyst.

The method comprises isomerizing the cyclobutene 1-carboxyl or 1-carbonyl derivative III to isomerized cyclobutene 1-carboxyl or 1-carbonyl derivative III′ in the presence of an olefin metathesis catalyst. The method further comprises contacting the cyclohexene derivative II with the isomerized cyclobutene 1-carboxyl or 1-carbonyl derivative III′ in the presence of an olefin metathesis catalyst. In certain embodiments of the invention, the cyclobutene III′ is prepared separately and treated with the cyclohexene II in the presence of an olefin metathesis catalyst to provide the polymer I. These polymerization methods enable the facile preparation of amphiphilic and bifunctional alternating polymers from simple and readily available starting materials.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the ¹H NMR spectra of amides 1c (top) and 1c′ (bottom) in CDCl₃.

FIG. 2 shows the HSQC spectrum of amide 1c′ in CDCl₃.

FIG. 3 shows the HSQC spectrum (upheld) of amide 1c′ in CDCl₃.

FIG. 4 shows the kinetic ¹³C NMR spectra of 1e isomerization in the presence of catalyst 2 (1:1 ratio) in CD₂Cl₂; (a) 70-90 min after mixing, (b) from bottom to top, spectra were obtained at 0-20 min, 40-55 min, 70-90 min, and 110-130 min.

FIG. 5 shows the HSQC spectrum of poly(1d′-alt-3)₅₀ in CD₂Cl₂.

FIG. 6 shows the partial ¹³C NMR spectra of AROMP polymers illustrate the absence of AA dyad or BB dyad ¹³C resonances.

FIG. 7 shows the ¹H NMR spectra of poly(1d′-alt-3)_(n) with (bottom) and without (top) deuterium labeling in CD₂Cl₂.

FIG. 8 shows the ¹H NMR spectrum of amide 1a in CDCl₃.

FIG. 9 shows the ¹³C NMR spectrum of amide 1a in CDCl₃.

FIG. 10 shows the partial ¹³C NMR spectrum of amide 1a in CDCl₃.

FIG. 11 shows the ¹H NMR spectrum of amide 1b in CDCl₃.

FIG. 12 shows the ¹³C NMR spectrum of amide 1b in CDCl₃.

FIG. 13 shows the ¹H NMR spectrum of amide 1c in CDCl₃.

FIG. 14 shows the ¹³C NMR spectrum of amide 1c in CDCl₃.

FIG. 15 shows the ¹H NMR spectrum of amide 1d in CD₂Cl₂.

FIG. 16 shows the ¹³C NMR spectrum of amide 1d in CDCl₃.

FIG. 17 shows ¹H NMR spectrum of amide 1e in CDCl₃.

FIG. 18 shows the ¹³C NMR spectrum of amide 1e in CDCl₃.

FIG. 19 shows the partial ¹³C NMR spectrum of amide 1e in CDCl₃.

FIG. 20 shows the ¹H NMR spectrum of amide 1f in CDCl₃.

FIG. 21 shows the ¹³C NMR spectrum of amide 1f in CDCl₃.

FIG. 22 shows the ¹H NMR spectrum of amide 1f* in CDCl₃.

FIG. 23 shows the ¹³C NMR spectrum of amide 1f* in CDCl₃.

FIG. 24 shows the ¹H NMR spectrum of amide 4 in CD₂Cl₂.

FIG. 25 shows the ¹³C NMR spectrum of amide 4 in CDCl₃.

FIG. 26 shows the partial ¹³C NMR spectrum of amide 4 in CDCl₃.

FIG. 27 shows the ¹H NMR spectrum of amide 1a′ in CDCl₃.

FIG. 28 shows the ¹H NMR spectrum of amide 1b′ in CDCl₃.

FIG. 29 shows the ¹H NMR spectrum of amide 1c′ in CDCl₃.

FIG. 30 shows the ¹³C NMR spectrum of amide 1c′ in CDCl₃.

FIG. 31 shows the partial ¹³C NMR spectrum of amide 1c′ in CDCl₃.

FIG. 32 shows the ¹H NMR spectrum of crude amide 1d and alkylidene 2 in CD₂Cl₂ with 100% 1d isomerized to 1d′.

FIG. 33 shows the ¹H NMR spectrum of amide 1e′ in CD₂Cl₂.

FIG. 34 shows the ¹H NMR spectrum of amide 1f and alkylidene 2 in CD₂Cl₂ with 90% 1f isomerized to 1f.

FIG. 35 shows the ¹H NMR spectrum of amide 1f* and 2 in CD₂Cl₂ with 79% 1f* isomerized to 1f*′.

FIG. 36 shows the ¹H NMR spectrum of amide 4 and alkylidene 2 in CD₂Cl₂. No isomerization is observed.

FIG. 37 shows the isomerization of 1c with and without 50 μL of MeOH in the presence of 2 in CD₂Cl₂. Spectra were obtained 1 hour after mixing monomer with catalyst.

FIG. 38 shows the isomerization of 1e with and without 50 equiv of 3-bromopyridine in the presence of 2 in CD₂Cl₂. Spectra were obtained 16 hours after mixing monomer and catalyst.

FIG. 39 shows the isomerization of 1e in the presence of Cl₂(H₂IMes)(PCy₃)Ru═CHPh (10 mol %) or alkylidene 2 (10 mol %) in CD₂Cl₂. Spectra were obtained 14 hours after mixing monomer and catalyst.

FIG. 40 shows the ¹H NMR spectrum of poly(1c′-alt-3)₁₀ in CD₂Cl₂.

FIG. 41 shows the ¹H NMR spectrum of poly(1c′-alt-3)₅₀ in CD₂Cl₂.

FIG. 42 shows the ¹H NMR spectrum of poly(1c′-alt-3)₁₀₀ in CD₂Cl₂.

FIG. 43 shows the ¹H NMR spectrum of poly(1c′-alt-3)₄₂₀ in CD₂Cl₂.

FIG. 44 shows the ¹³C NMR spectrum of poly(1c′-alt-3)₄₂₀ in CD₂Cl₂.

FIG. 45 shows the ¹H NMR spectrum of poly(1b′-alt-3)₁₄₀ in CD₂Cl₂.

FIG. 46 shows the ¹H NMR spectrum of poly(1b′-alt-3)₂₆₀ in CD₂Cl₂.

FIG. 47 shows the ¹³C NMR spectrum of poly(1b′-alt-3)₂₆₀ in CD₂Cl₂.

FIG. 48 shows the ¹H NMR spectrum of poly(1a′-alt-3)₅₀ in CDCl₃.

FIG. 49 shows the ¹H NMR spectrum of poly(1a′-alt-3)₁₀₀ in CD₂Cl₂.

FIG. 50 shows the ¹³C NMR spectrum of poly(1a′-alt-3)₁₀₀ in CD₂Cl₂.

FIG. 51 shows the ¹H NMR spectrum of poly(1d′-alt-3-D₁₀)₁₀ in CD₂Cl₂.

FIG. 52 shows the ¹H NMR spectrum of poly(1d′-alt-3)₅₀ in CD₂Cl₂.

FIG. 53 shows the ¹³C NMR spectrum of poly(1d′-alt-3)₅₀ in CD₂Cl₂.

FIG. 54 shows the APT spectrum of poly(1d′-alt-3)₅₀ in CD₂Cl₂.

FIG. 55 shows the molar mass dispersity (

_(M)) traces of isomerized amide AROMP polymers. Phenogel 5 μm MXL LC column (300×7.8 mm, 100 KDa exclusion limit), Phenomenex, was used with a flow rate of 0.7 mL/min in methylene chloride at 30° C. 50-mers of 1c′ and 1d′ were prepared in a one-pot procedure from 1c or 1d. All others were prepared with isomerized and purified amides.

FIG. 56 shows the molar mass dispersity (

_(M)) traces of long linear isomerized amide AROMP polymers. Phenogel 5 μm 10E4A, LC column (300×7.8 mm, 500 KDa exclusion limit), Phenomenex, was used with a flow rate of 1.00 mL/min in THF at 30° C. Both polymers were prepared with isomerized and purified amides.

FIG. 57 shows the ¹H NMR spectra of the alkene and aromatic region of i-AROMP starting material, intermediate, and product. (a) Monomer 1c in CDCl₃; (b) Formation of the tetrasubstituted isomer 1c′ in the presence of catalyst 2 in CDCl₃; (c) Alternating copolymer poly(1c′-alt-3)₄₂₄ formed upon addition of cyclohexene 3 to 1c′ in CD₂Cl₂. CD₂Cl₂ was used to avoid overlap with aromatic proton signals and to allow their integration. The two alkene signals correspond to H1 and H4 of poly (1c′-alt-3)₄₂₄.

FIG. 58 shows the alkene region of the HSQC spectrum of poly(1d′-alt-3)₅₀ in CD₂Cl₂. The polymer backbone has only four alkene carbons and two alkene hydrogens corresponding to C1-C4 and H1 and H4 in Scheme 1.

DETAILED DESCRIPTION OF THE INVENTION

Most sequence-controlled polymers lack rigorous fidelity, e.g. the chain microstructures are not completely well controlled or they are homo polymers with simple chain microstructures or copolymers, such as random or block copolymers, in which the monomer sequence is not precisely controlled. Polymers of imprecise sequence are widely employed, but do not provide the same structural and functional complexity as sequence-controlled biopolymers created by nature. The present method provides a facile approach to prepare long and alternating AB copolymers. According to the present method, these copolymers may be formed in a single reaction mixture in which isomerization occurs first, followed by alternating ring-opening cross metathesis of type A monomer and ring opening cross metathesis of type B monomer.

Accordingly, the invention provides methods for the preparation of polymers in which the backbone chain has a regular alternating pattern of functional group arrangement. The method further allows for the preparation of copolymers having low polydispersities and long lengths.

The invention provides an alternating AB copolymer and a method for producing an alternating AB copolymer comprising the repeating unit I,

The method comprises the polymerization of cyclobutene derivative III′ and cyclohexene derivative II in the presence of an olefin metathesis catalyst. In embodiments of the process that use the cyclobutene III, the process further comprises isomerizing a cyclobutene of structure III in the presence of an olefin metathesis catalyst to form a cyclobutene III′ and contacting an olefin of structure II with an isomerized cyclobutene III′

in the presence of an olefin metathesis catalyst.

In the above structures: R may be, but is not limited to, H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₁-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₁-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group. In certain embodiments, the repeating unit, n, is between 2 and 500. Each substituent R¹ through R⁶ may independently be selected from, but is not limited to, H, aldehyde, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₆ cycloalkyl, aryl, heterocyclyl, C₁-C₂₀ alkoxy, C₁-C₂₀ acyloxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino, or halogen. It is understood that any carbon-carbon double bonds in R^(a) or in R¹ through R⁶ are essentially unreactive toward metathesis reactions with the catalyst. It will be also understood that adjacent substitutions of R¹-R⁶ may be taken together to form a 5- to 7-membered ring which may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group.

In preferred embodiments of the invention, R⁵ and R⁶ are taken together to form a 5- or 6-membered ring, which may optionally contain up to 2 heteroatoms in the ring selected from O or N, and which may be unsubstituted or substituted with up to four substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group. In particularly preferred embodiments, R⁵ and R⁶ are taken together to form a cyclohexyl ring, which may be optionally substituted.

In certain embodiments, the invention provides a method for producing an alternating AB copolymer comprising the repeating unit Ia

In the above structures, X may be either O or NH, and is preferably NH; and R^(a) may be, but is not limited to, H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₁-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group. In certain embodiments, the repeating unit, n, is between 2 and 500. Each substituent R¹ through R⁶ may independently be, but is not limited to, H, aldehyde, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₆ cycloalkyl, aryl, heterocyclyl, C₁-C₂₀ alkoxy, C₁-C₂₀ acyloxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino, or halogen. It is understood that any carbon-carbon double bonds in R^(a) or in R¹ through R⁶ are essentially unreactive toward metathesis reactions with the catalyst. It will be also understood that adjacent substitutions of R¹-R⁶ may be taken together to form a 5- to 7-membered ring which may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group.

In preferred embodiments of the invention, R⁵ and R⁶ are taken together to form a 5- or 6-membered ring, which may optionally contain up to 2 heteroatoms in the ring selected from O or N, and which may be unsubstituted or substituted with up to four substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group. In particularly preferred embodiments, R⁵ and R⁶ are taken together to form a cyclohexyl ring, which may be optionally substituted.

In a preferred embodiment, the invention provides a method for producing an alternating AB copolymer comprising the repeating unit Ib

In the above structure, R^(b) may be, but is not limited to, H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₁-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₁-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group, with the proviso that any carbon-carbon double bonds in R^(b) are essentially unreactive toward metathesis reactions with the catalyst. In certain embodiments, the repeating unit, n, is between 2 and 500.

In certain embodiments, the invention provides a method for producing an alternating AB copolymer from a monomer comprising a cyclohexene of structure IIa

In the above structures, each substituent R² and R³ may independently be, but is not limited to, H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₁-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino or halogen, and may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group; with the proviso that any carbon-carbon double bonds in R² and R³ are essentially unreactive toward metathesis reactions with the catalyst. It will be also understood that R² and R³ may be taken together to form a 5- to 7-membered ring which may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group.

In a preferred embodiment, the invention provides a method for producing an alternating AB copolymer from a monomer comprising a cyclohexene of structure

In certain embodiments, the invention provides a method for producing an alternating AB copolymer from a monomer comprising an cyclobutene of structure IIIa or IIIa′, in which the cyclobutene of structure Ma is isomerized to a cyclobutene of structure IIIa′

in the presence of an olefin metathesis catalyst.

In the above structures, X may be either O, or NH, and R^(a) may be, but is not limited to, H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₁-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₁-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group. Each substituent R⁵ and R⁶ may independently be, but is not limited to, H, aldehyde, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₆ cycloalkyl, aryl, heterocyclyl, C₁-C₂₀ alkoxy, C₁-C₂₀ acyloxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino, or halogen. It is understood that any carbon-carbon double bonds in R^(a), R⁵ or R⁶ are essentially unreactive toward metathesis reactions with the catalyst. It will be also understood that R⁵ and R⁶ may be taken together to form a 5- to 7-membered ring which may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group.

In certain embodiments, the invention provides a method for producing an alternating AB copolymer from a monomer comprising an cyclobutene of structure IIIb or IIIb′, in which the cyclobutene of structure IIIb is isomerized to a cyclobutene of structure IIIb′

in the presence of an olefin metathesis catalyst.

In the above structures, R^(b) may be, but is not limited to, H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₁-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₁-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group. Each substituent R⁵ and R⁶ may independently be, but is not limited to, H, aldehyde, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₆ cycloalkyl, aryl, heterocyclyl, C₁-C₂₀ alkoxy, C₁-C₂₀ acyloxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino, or halogen. It is understood that any carbon-carbon double bonds in R^(a), R⁵ or R⁶ are essentially unreactive toward metathesis reactions with the catalyst. It will be also understood that R⁵ and R⁶ may be taken together to form a 5- to 7-membered ring which may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group.

In preferred embodiments of the invention, for each of IIIa, IIIa′, IIIb, IIIb′, R⁵ and R⁶ are taken together to form a 5- or 6-membered ring, which may optionally contain up to 2 heteroatoms in the ring selected from O or N, and which may be unsubstituted or substituted with up to four substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group. In particularly preferred embodiments, R⁵ and R⁶ are taken together to form a cyclohexyl ring, which may be optionally substituted.

In a preferred embodiment, the invention provides a method for producing an alternating AB copolymer from a monomer comprising an cyclobutene of structure IIIc or IIIc′, in which the cyclobutene of structure IIIc is isomerized to a cyclobutene of structure IIIc′

in the presence of an olefin metathesis catalyst.

In the above structures, R^(b) may be, but is not limited to, H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₁-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₁-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group. It will be understood that m may be between 0 and 4, and that for each m, the substituent R⁸ may independently be, but is not limited to, aldehyde, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₆ cycloalkyl, aryl, heterocyclyl, C₁-C₂₀ alkoxy, C₁-C₂₀ acyloxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino, or halogen. It is understood that any carbon-carbon double bonds in R^(b) or R⁸ are essentially unreactive toward metathesis reactions with the catalyst. It will be also understood that adjacent substitutions of R⁸ may be taken together to form a 5- to 7-membered ring which may be optionally substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group.

By way of example, suitable cyclohexene and cyclobutene species include but are not limited to the following:

It will be understood that any olefins or other functional groups in the substituents of the A and B monomers should be essentially unreactive with the metathesis catalyst under the reaction conditions, so that the metathesis polymerization involves the cyclobutene and cyclohexene double bonds exclusively, or nearly so. Generally, any carbon-carbon double bonds in R or in R¹ through R⁶ should be trisubstituted or tetrasubstituted, or otherwise rendered unreactive with the catalyst.

Aryl, as used herein, includes but is not limited to optionally substituted phenyl, naphthyl, anthracenyl, and phenanthryl groups. Heterocycle and heterocyclyl refer to monocyclic and fused polycyclic heteroaromatic and heteroaliphatic ring systems containing at least one N, O, S, or P atom. Aryl and heterocyclic groups may contain from 1 to 60 carbon atoms, and may range from furan, thiophene, and benzene to large chromophores such as phthalocyanines and fullerenes. For some applications, aryl and heterocyclic groups will preferably contain from 1 to 20 carbon atoms.

It will be apparent that alkyl, alkenyl, cycloalkyl, heterocyclyl, acyl, and aryl moieties in the substituents R and R¹ through R⁶ may be substituted with functional groups known to be compatible with the catalyst. Examples include, but are not limited to, C₁-C₄ acyl, acyloxy, acylamino, amido, aryloxy, alkoxy and alkylthio groups; halogens; protected amino groups such as BocNH— and FmocNH—; protected hydroxy groups such as TMSO—, BzO—, and BnO—; and protected carboxyl groups such as —CO₂-t-Bu and —CO₂Bn. Accordingly, the terms alkyl, alkenyl, cycloalkyl, acyl, aryl, and heterocyclyl as used herein encompass such substituents.

The method may be used to prepare rigorously alternating AB copolymers. In the copolymers of the present invention, an A monomer derived from a cyclobutene derivative III selected from a compound of formula III, IIIa, IIIb and IIIc alternates with a B monomer selected from a cyclohexene derivative II or IIa. In certain embodiments of the invention, the cyclobutene III is isomerized to provide the cyclobutene III′ which is followed by the polymerization with the cyclohexene in the presence of an olefin metathesis catalyst to provide the AB polymer. These reactions may be run in a single reaction vessel.

In certain other embodiments of the invention, the cyclobutene III′, IIIa′, IIIb′ and IIIc′ is prepared separately. The cyclobutene III′, IIIa′, IIIb′ and IIIc′ is treated with the cyclohexene II or IIa in the presence of an olefin metathesis catalyst to provide the AB copolymer.

The catalyst may be any olefin metathesis catalyst known in the art, such as those disclosed in WO 03/070779. It is preferably an alkylidene ruthenium complex, and more preferably a complex of formula (L)₂(L′)X₂Ru═CHR′, wherein R′ may be, for example, H, C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₃-C₆ cycloalkyl, or aryl. The ligand L is typically a trialkyl phosphines, triarylphosphines, tri(cycloalkyl)phosphines, pyridines, aryl, wherein aryl is optionally substituted with a halogen. L′ is a second ligand, and may be a trialkyl phosphine, triarylphosphine, tri(cycloalkyl)phosphine, or a pyridine. L′ may also be an imidazolin-2-ylidine carbene of formula IV:

wherein R⁹ may be selected from the group, but is not limited to a C₁-C₆ alkyl group or aryl. In certain embodiments, X is a halogen or pseudohalogen such as F, Cl, Br, NO₃, CF₃, or CF₃COO⁻.

In certain embodiments, L is a pyridine, optionally 3-bromopyridine; and L′ is an imidazolin-2-ylidine carbene. In another embodiment, R⁹ is preferably mesityl, 2-methylphenyl, 2-ethylphenyl, 2-isopropylphenyl, 2,3-diisopropylphenyl, 2,6-difluorophenyl, or 3,5-di-t-butylphenyl.

The polymers of the present invention may be prepared according to the representative Scheme 1.

We tested the corresponding bicyclo[4.2.0]oct-7-ene-7-carboxamides 1a-f in ROMP reactions with the Grubbs III catalyst 2 (Scheme 1). Surprisingly, under ROMP conditions, each of the amides 1 isomerized to the bicyclo[4.2.0]oct-1(8)-ene-8-carboxamide 1′. None of the amides showed evidence of homopolymerization in the presence of catalyst 2.

On the other hand, addition of cyclohexene 3 to isomerized amides 1′ in the presence of catalyst 2 provided a reaction manifold for the isomerized amides that led to linear, alternating copolymers, poly(1′-alt-3)_(n), of impressive length. We now refer to this tandem reaction as i-AROMP for isomerization, alternating ring-opening metathesis polymerization.

Alternatively, bicyclo[4.2.0]oct-1(8)-ene-8-carboxamides can be prepared from bicyclo[4.2.0]oct-1(8)-ene-8-carboxylic acids prepared by methods known in the art. See (i) Fleming, I.; Harley-Mason, J. J. Chem. Soc. 1964, “403. The reaction of enamines with electrophilic olefins. A synthesis of cyclobutanes,” 2165-2174. DOI: 10.1039/JR9640002165; (ii) Banwell, M. G.; Vogt, F.; Wu, A. W. Australian Journal of Chemistry 2006, “Assembly of the 1-Azaspiro[5.5]undecane Framework Associated with Perhydrohistrionicotoxin via Electrocyclic Ring-Opening of a Ring-Fused gem-Dichlorocyclopropane and Trapping of the Resulting π-Allyl Cation by a Tethered, Nitrogen-Centered Nucleophile,” 59, 415-425. DOI: http://dx.doi.org/10.1071/CH06218.

EXAMPLES

The following examples further illustrate the invention, but should not be construed to limit the scope of the invention in any way.

All metathesis reactions were performed under an N₂ atmosphere. Solvents, e.g. CH₂Cl₂ and THF were purified with Pure Process Technology (PPT). Deuterated solvents for all ring-opening reactions were degassed and filtered through basic alumina before use. Catalyst Cl₂(H₂IMes)(PCy₃)Ru═CHPh was purchased from Aldrich. Cyclohexene-D₁₀ was purchased from CDN Isotope Inc. The synthesis of catalyst (3-Br-Pyr)₂Cl₂(H₂IMes)Ru═CHPh, 2, was performed according to the procedure of Love et al. (Love, J. A.; Morgan, J. P.; Trnka, T. M.; Grubbs, R. H. Angew. Chem. Int. Ed. 2002, 41, 4035-4037). Experimental procedures for the preparation of amides 1 and 4 are below.

Solvents, e.g. CH₂Cl₂ and THF were purified with Pure Process Technology (PPT). Mallinckrodt silica gel 60 (230-400 mesh) was used for column chromatography. Analytical thin layer chromatography (TLC) was performed on precoated silica gel plates (60F₂₅₄), flash chromatography on silica gel-60 (230-400 mesh), and Combi-Flash chromatography on RediSep normal phase silica columns (silica gel-60, 230-400 mesh). Bruker Nanobay 400, Avance III 500, Avance III 700 NMR instruments were used for analysis. Chemical shifts were calibrated from residual undeuterated solvents; they are denoted in ppm (δ). Molecular weights and molar-mass dispersities except poly(1c′-alt-3)₄₂₄ were measured with a gel phase chromatography system constructed from a Shimadzu pump coupled to a Shimadzu UV detector. THF served as the eluent with a flow rate of 0.700 mL/min on a Phenogel 5μ MXL GPC column (10⁵ Da exclusion limit), Phenomenex. The dispersity of poly(1c′-alt-3)₄₂₄ was measured on a size exclusion chromatography system constructed from a GPCmax VE-2001 pump coupled to a model 305 TDA detector. CHCl₃ served as the eluent with a flow rate of 1.00 mL/min on a TSKgel GMH_(HR)-H(S) column (13 μm, 4×10⁸ exclusion limit). Both GPCs were calibrated with poly(styrene) standards at 30° C. The T_(g) was measured by differential scanning calorimetry (DSC) using a Perkin-Elmer DSC-7 thermal analysis system (Shelton, Conn., USA), at a scan rate of 10° C./min. Polymer samples (each weighing approx. 1.2 mg) were sealed in aluminum cassettes under dry conditions.

Example 1: Synthesis of Monomers

Bicyclo[4.2.0] and [3.2.0] esters were synthesized by a modification of Snider's approach (Snider, B. B.; Rodini, D. J.; Cionn, R. S. E.; Sealfon, S. J. Am. Chem. Soc. 1979, 101, 5283-5493) as previously described. (Tan, L.; Parker, K. A.; Sampson, N. S. Macromolecules 2014, 47, 6572-6579). Basic hydrolysis provided the carboxylic acids that were coupled to selected amines to yield amides 1a-1e and 4. Diastereomers 1f and 1f* were prepared from the mixture of racemic bicyclo[4.2.0]oct-7-ene-7-carboxylic acid and (S)-phenylglycinol, separated, and then, individually acylated. Relative stereochemistry was not assigned to the diastereomers.

Example 2: Attempted ROMP of Bicycloamides: Discovery of Isomerization

We submitted the bicyclo[4.2.0] amides 1 to ROMP conditions with catalyst 2 in CDCl₃ and monitored the reactions by ¹H NMR. The bicyclic monomers underwent rapid reactions. The olefinic proton signals at ˜6.7 ppm disappeared or nearly disappeared (FIGS. 57a and b ) within 15 minutes to 24 hours (Table 1, entries 1-7). However, no polymerization could be detected. In contrast, when amide 4 was stirred with catalyst 2 for 18 hours at 25° C., only a 2% decrease in the intensity of the olefinic resonance was observed.

The products derived from monomers 1c and 1d were selected for further study. Purification yielded compounds 1c′ and 1d′ with molecular masses identical to those of the starting materials. The spectroscopic signatures of 1c′ and 1d′ were distinct from those of 1c and 1d indicating that isomerization had occurred. Relative to the ¹ H NMR spectra of the starting materials, those of 1c′ and 1d′ contained one more methylene proton signal, one less methine signal, and no olefinic proton resonance (FIGS. 57 and 1). Further spectroscopic characterization of 1c′ by HSQC NMR spectroscopy indicated that it retains the unsaturated bicyclic structure of 1c, but that the double bond had migrated (Scheme 1 and FIGS. 2-3).

TABLE 1 Isomerization of amides effected by catalyst 2. Time % entry 1 [1]:[cat] Catalyst/additive (h) conv^(b) 1 1a 20:1^(a) 2 16 90 2 1b 50:1^(a) 2 8 95 3 1c 50:1^(a) 2 1.5 100 4 1d 20:1^(a) 2 0.3 100 5 1e 50:1^(a) 2 6 100 6 1f 10:1^(a) 2 24 70 7 1f* 10:1^(a) 2 24 90 8 1e 10:1^(c) 2 14 100 9 1e 10:1^(c) 2/3-Br-pyridine 14 35 (50 eq) 10 1e  5:1^(a) 2 1 100 11 1e  5:1^(a) (Cl)₂(H₂IMes)(PCy₃)Ru═CHPh 14 5 12 1e 10:1^(c) 2/1,4-benzoquinone 14 100 (5 eq) 13 1c 10:1^(c) 2 1.5 100 14 1c 10:1^(c) 2/8% MeOH 24 65 ^(a)[cat] = 0.01M, CD₂Cl₂, 35° C. ^(b)% conv was determined by monitoring the monomer alkene resonances in ¹H NMR spectra. ^(c)[cat] = 0.005M, CD₂Cl₂, 35° C.

Typically, tetra-substituted olefins are not obtained with catalyst 2. (Stewart, I. C.; Ung, T.; Pletnev, A. A.; Berlin, J. M.; Grubbs, R. H.; Schrodi, Y. Org. Lett. 2007, 9, 1589-1592; Berlin, J. M.; Campbell, K.; Ritter, T.; Funk, T. W.; Chlenov, A.; Grubbs, R. H. Org. Lett. 2007, 9, 1339-1342; Rost, D.; Porta, M.; Gessler, S.; Blechert, S. Tetrahedron Lett. 2008, 49, 5968-5971; Ackermann, L.; Fürstner, A.; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787-4790). In our system, further isomerization to the bicyclo[4.2.0]oct-1(2)-ene-8-carboxamide is unfavorable because in this compound the alkene is not in conjugation with the amide. We observed that the bicyclo[3.2.0] system 4 does not undergo appreciable isomerization. As noted above, regioisomer 4′ is not formed upon addition of catalyst 2 to amide 4.

Example 3: Mechanism of Isomerization

Control experiments support the role of species 2 as the isomerization catalyst. No isomerization was observed upon incubation of 1c in CH₂Cl₂ at 35° C. for 16 hours in the absence of catalyst 2. Over the course of our experiments, we utilized four different batches of 2. All four preparations of 2 catalyzed isomerization to the same extent and at the same rate. Furthermore, addition of 50 equivalents of 3-bromopyridine to amide 1e and catalyst 2 reduced the percentage of isomerization 3-fold over a 14-hour time period as compared to isomerization in the absence of exogenous 3-bromopyridine ([2]=0.005 M, Table 1, entry 8 vs 9). Likewise, we found that 20 mol % of (Cl)₂(H₂IMes)(PCy₃)Ru═CHPh, for which PCy₃ ligand dissociation is less favored, catalyzed less than 5% isomerization of amide 1e in 14 hours as compared to 100% conversion with 20 mol % catalyst 2 within 1 hour (Table 1, entry 10 vs 11). These experiments indicate that coordination of the substrate to the Ru catalyst is involved in the isomerization.

Cyclobutenes are sensitive to acid-catalyzed decomposition and/or reaction. In order to exclude the possibility that substrates 1 were being converted to isomers 1′ by adventitious acid, we repurified the monomers by passing them through dry basic alumina before subjecting them to catalyst 2. The isomerization rates and product distributions were unchanged.

Ruthenium catalysts promote olefin isomerization. Previous reports (Cadot, C.; Dalko, P. I.; Cossy, J. Tetrahedron Lett. 2002, 43, 1839-1841; Dinger, M. B.; Mol, J. C. Organometallics 2003, 22, 1089-1095; Dinger, M. B.; Mol, J. C. Eur. J. Inorg. Chem. 2003, 2003, 2827-2833; Schmidt, B. Eur. J. Org. Chem. 2004, 2004, 1865-1880) have proposed that either a Ru hydride species (McGrath, D. V.; Grubbs, R. H. Organometallics 1994, 13, 224-235; Bourgeois, D.; Pancrazi, A.; Nolan, S. P.; Prunet, J. J. Organomet. Chem. 2002, 643-644, 247-252; van Rensburg, W. J.; Steynberg, P. J.; Meyer, W. H.; Kirk, M. M.; Forman, G. S. J Am. Chem. Soc. 2004, 126, 14332-14333; van Rensburg, W. J.; Steynberg, P. J.; Kirk, M. M.; Meyer, W. H.; Forman, G. S. J. Organometallic Chem. 2006, 691, 5312-5325; Ashworth, I. W.; Hillier, I. H.; Nelson, D. J.; Percy, J. M.; Vincent, M. A. Eur. J Org. Chem. 2012, 2012, 5673-5677) or a π-allyl Ru complex (McGrath, D. V.; Grubbs, R. H. Organometallics 1994, 13, 224-235; Bourgeois, D.; Pancrazi, A.; Nolan, S. P.; Prunet, J. Organomet. Chem. 2002, 643-644, 247-252; Higman, C. S.; Plais, L.; Fogg, D. E. Chem. Cat. Chem 2013, 5, 3548-3551; Schmidt, B. J. Mol. Catal. A: Chem. 2006, 254, 53-57; Trost, B. M.; Kulawiec, R. J. J. Am. Chem. Soc. 1993, 115, 2027-2036) is responsible. The Ru hydride can form upon decomposition that occurs with extended reaction times or extreme reaction conditions. (Dinger, M. B.; Mol, J. C. Organometallics 2003, 22, 1089-1095; Dinger, M. B.; Mol, J. C. Eur. J. Inorg. Chem. 2003, 2003, 2827-2833). The rapid isomerization rates we observe are inconsistent with the formation of a Ru hydride species through decomposition of 2. Moreover, we did not observed Ru hydride resonances at the expected upheld region between 0 and −30 ppm in the ¹H NMR spectra of the above reactions. Addition of 1,4-benzoquinone, which has been reported to oxidize Ru hydride species and prevent olefin isomerization, (Hong, S. H.; Sanders, D. P.; Lee, C. W.; Grubbs, R. H. J. Am. Chem. Soc. 2005, 127, 17160-17161), to our amide le did not suppress isomerization. Therefore, a reduced, electron-rich species is unlikely to be responsible for initiation of isomerization (Table 1, entry 8 vs 12).

Alcohols can act as ruthenium reducing agents to enhance Ru hydride formation. (Higman, C. S.; Plais, L.; Fogg, D. E. Chem. Cat. Chem 2013, 5, 3548-3551). However, their coordination with Ru can suppress isomerization that proceeds via a π-allyl mechanism. (Schmidt, B. J. Mol. Catal. A: Chem. 2006, 254, 53-57; Bielawski, C.; Scherman, O.; Grubbs, R. Polymer 2001, 42, 4939-4945; Hillmyer, M. A.; Nguyen, S. T.; Grubbs, R. H. Macromolecules 1997, 30, 718-721). Therefore, we tested isomerization of 1c with and without methanol in the presence of 10 mol % catalyst 2. The 1c isomerization reaction containing 8% methanol in CD₂Cl₂ proceeded much more slowly than the reaction without methanol; only 65% isomerization was observed over 24 hours as compared to complete isomerization in 1.5 hours in the absence of methanol (Table 1, entry 13 vs 14). Our observations are consistent with isomerization via a π-allyl Ru complex formed upon coordination of amide 1 with catalyst 2. Evidence in hand does not distinguish between direct formation of this species from amide 1 or its formation by a “ring-walking” mechanism. (Curran, K.; Risse, W.; Hamill, M.; Saunders, P.; Muldoon, J.; Asensio de la Rosa, R.; Tritto, I. Organometallics 2012, 31, 882-889).

The isomerization rate depends on the nature of the amide nitrogen substituent: 1d>1c>1e>1b>1a>1f/1f*. The rate is slower for amides of α-substituted amines and for amides of amines that include an ester in the alkyl chain.

To investigate further the electronic influence on isomerization, we undertook a control experiment to establish the amount of isomerization with the corresponding methyl bicyclo[4.2.0]oct-7-ene-7-carboxylate. When subjected to catalyst 2 (2 mol %) at 50° C. for 2 days, the ester underwent ROM without isomerization as judged by the disappearance of the catalyst alkylidene proton signal and the remaining signals for the ester starting material. Therefore, the amide moiety assists rapid equilibration of isomers of 1 in the presence of 2.

Without being limited by theory, the kinetic data taken together with the structure-activity data strongly support a mechanism in which equilibration of regioisomers takes place via initial coordination involving the amide functional group and subsequent formation of a transient Ru π-allyl species.

Example 4: Alternating Ring-Opening Metathesis Polymerization of i-Amides

We monitored the isomerization of amide 1e to amide 1e′ in the presence of 1 equivalent of catalyst 2 by ¹³C NMR spectroscopy. In addition to the growth of the signals corresponding to the formation of amide 1e′, remarkably we observed the appearance of new peaks at 322.3 and 178.5 ppm, presumably representing the carbene carbon and the amide carbon respectively in the [Ru]═C(R)CONHR′ species (FIG. 4). We also observed a peak at 315.5, representing a second ruthenium carbene species. On the basis of this experiment, we concluded, much to our surprise since monomer 1e′ is a tetra-substituted alkene, that ROM occurs upon formation of 1′. Unlike the ruthenium carbenes from amide-substituted cyclobutenes, previously studied in our laboratory, (Lee, J. C.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2006, 128, 4578-9; Song, A.; Lee, J. C.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2010, 132, 10513-10520) the amide-substituted carbene derived from 1′ does not undergo metathesis with remaining monomer, as noted above.

We reasoned that the amide-substituted carbene derived from 1′ might undergo ring-opening cross-metathesis with cyclohexene 3, in a reaction analogous, but not identical, to the reaction of Ru enoic carbenes in our previous AROMP work. (Song, A.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2009, 131, 3444-3445; Lee, J. C.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2006, 128, 4578-9; Romulus, J.; Tan, L.; Weck, M.; Sampson, N. S. Macromol. Lett. 2013, 2, 749-752; Tan, L.; Parker, K. A.; Sampson, N. S. Macromolecules 2014, 47, 6572-6579). Indeed, copolymer was rapidly formed upon addition of cyclohexene 3 (Table 2). The copolymerization of monomer 1c′ or 1d′ with 3, yields a 50-AB-mer in approximately 2 hours. Remarkably, in light of the steric hindrance in the system, this AROMP is faster under similar conditions than that of the less hindered 1-cyclobutene carboxylic methyl ester/cyclohexene AROMP which yields a 50-AB-mer in 3 hours (Song, A.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2009, 131, 3444-3445) and that of the corresponding bicyclo[4.2.0]oct-7-ene-7-carboxylic ester which yields a 50-AB-mer in 8 hours. (Tan, L.; Parker, K. A.; Sampson, N. S. Macromolecules 2014, 47, 6572-6579).

¹H NMR spectroscopy of the copolymers displayed two alkene signals consistent with product from AROMP of isomer 1′. In contrast, AROMP of the original amide 1 would have given copolymer for which the NMR spectrum displayed three alkene signals (Scheme 1).

In order to investigate the possibility of AROMP of the original amide 1c, we premixed cyclohexene 3 with catalyst 2 before addition of amide. However, no polymer resonances were detected before a significant amount of amide 1c had isomerized to amide 1c′. Furthermore, the polymer obtained was identical to poly(1c′-alt-3)₁₀ as judged by comparison of the ¹H NMR spectra. Therefore, isomerization of 1c is faster than ROM, and thus faster than ROMP or AROMP of 1c. Likewise, in the case of amide 1d, isomerization to amide 1d′ was complete before polymer appeared.

In the cases of 1a, 1b, 1e, and one of the diastereomers of 1f/1f*, we obtained mixtures of starting materials and alternating polymers. In these systems, then, the rate of isomerization is slower than or similar to the rate of ROM. Owing to their fast isomerization and polymerization, amides 1c′ and 1d′ were selected for the further characterization of their AROMP products. Polymers poly(1c′-alt-3)₉₇, poly(1c′-alt-3)₄₂₄, and poly(1d'-alt-3)₅₀ were fully characterized.

Analysis of poly(1d′-alt-3)₅₀ by ¹H NMR, ¹³C NMR, APT and HSQC spectroscopy revealed that the polymer backbone has four alkene carbons and two alkene hydrogens corresponding to C1-C4 and H1 and H4 (Scheme 1, FIG. 5). HSQC spectroscopy confirmed that the amide-substituted olefin is a single stereoisomer; there is a single H1 signal, at 6.29 ppm that correlates with C1 at 136 ppm (FIG. 2). On the basis of comparison of the H1 alkene chemical shift with model compounds, we conclude that the conjugated alkene is of E-configuration. A single H4 signal at 5.11 ppm correlates with C4 at 121 ppm. Because of peak broadening in the polymer, we could not determine if the C3-C4 alkene is stereoregular.

Integration of the poly(1′-alt-3)_(n) alkene signals relative to side chain signals demonstrated that an equal incorporation of the two monomers had occurred. An AA or BB dyad would be formed upon backbiting. Additional alkene proton resonances in the 5 ppm region of the ¹H NMR spectrum which would indicate formation of BB dyad were not observed. In the i-AROMP product, the AA dyad does not possess an alkene proton. Therefore, we inspected the ¹³C NMR spectra of poly(1d′-alt-3)₅₀ and poly(1c′-alt-3)₄₂₄ for the presence of AA dyad alkene resonances, specifically, a C3′ resonance between 160-145 ppm, and found none (FIG. 6). Further evidence for the equal incorporation of monomers 1d′ and 3 was obtained with experiments with cyclohexene-D₁₀. The ¹H NMR spectra of the deuterium labeled copolymer poly(1d′-alt-3-D₁₀)₁₀ show a complete loss of the alkene resonances at 6.3 ppm and 5.1 ppm as expected for an alternating AB polymer (FIG. 7).

TABLE 2 Alternating copolymerization (AROMP) of bicyclic amides 1 or 1′ and cyclohexenes 3 catalyzed by catalyst 2.^(a) time % M_(w) ^(GPC,d) M_(n) ^(GPC,d) M_(n) ^(theor,e) entry A/B [A]:[3]:[2] [2] (M) (h) conv^(b) DP_([AB]) ^(c) (kDa) (kDa) D_(M) (kDa) 1 1c/3  10:20:1 0.01 1.5 100 10 nd^(f) nd nd nd 2 1c/3  50:100:1 0.002 2 100 50 17.0 9.4 1.8 14.5 3 1d/3  50:100:1 0.002 1 100 ^(g) 16.0 10.1 1.6 15.6 4^(h) 1a′/3  50:100:1 0.002 2 100 50 15.1 12.5 1.2 15.8 5^(h) 1a′/3 100:200:1 0.002 6 100 100 30.7 29.1 1.1 31.9 6^(h) 1b′/3 150:300:1 0.002 2.5 100 140 40.3 34.0 1.2 45.7 7^(h) 1b′/3 300:600:1 0.001 3.5 90 260 80.9 69.6 1.2 91.0 8^(i) 1c′/3 100:200:1 0.002 2 100 100 28.4 20.5 1.4 28.1 9^(i) 1c′/3 500:1000:1 0.0004 6 85 420 130.9 111.6 1.2 137.7 ^(a)All preparative polymerization experiments were performed three times. Representative molecular weight data are presented from a single polymerization. ^(b)Conversion was determined by monitoring the disappearance of the amide resonance in 1 or 1′. ^(c)Degree of polymerization (DP) was determined for the AB repeat by integration of polymer resonances relative to the styrene end group. We estimate the integration error to be within 5%. ^(d)M_(w)-weight average molecular weight; M_(n)-number average molecular weight, determined by GPC. ^(e)Theoretical M_(n) calculated from the monomer:catalyst feed ratio. ^(f)not determined. ^(g)The DP could not be determined because of spectroscopic overlap and was estimated from the feed ratio of 1d and catalyst 2. ^(h)hisomerized amide was isolated and fresh 2 added before AROMP in CDCl₃. ^(i)Isomerized amide was isolated and fresh 2 added before AROMP in CD₂Cl₂.

We explored the utility of alternating copolymerization by testing the maximal length of alternating copolymer that could be prepared. When cyclohexene 3 was added directly to a completed isomerization reaction of 1c′ or 1d′, poly(1c′-alt-3)50 or poly(1d′-alt-3)50 was obtained (Table 2). However, the dispersities exceeded those expected from the monomer:—catalyst ratio for a ruthenium-catalyzed polymerization, presumably because of loss of catalyst during isomerization. Therefore, in order to facilitate characterization of polymers longer than 100 AB dyads, to maximize their purity, and to minimize their dispersity, we isolated amides 1′ before initiation of the AROMP reaction and added fresh catalyst.

In the case of amides 1a′ and 1b′, the AROMP reactions provided maximal lengths of 100 AB dyads and 260 AB dyads, respectively; with modest D_(M)=1.1-1.2. Higher monomer feed ratios did not provide longer copolymers. In contrast, when amide 1c′ was mixed with catalyst 2 in a ratio of 500:1 with 1000 equivalents of cyclohexene 3, we reproducibly obtained alternating copolymer with more than 400 AB dyads (FIG. 57c ) and a modest molecular weight distribution (D_(M)=1.2). Although the isomerization of 1d to 1d′ was facile, the length of the copolymers obtained was limited to 50 AB dyads regardless of whether amide 1d′ or 1d was used to initiate propagation. Finally, amides 1e′ and if provided only short alternating copolymers that were not characterized further. Overall propagation efficiencies in order are 1c′>1b′>1a′>1d′>1e′>1f′. Thus, the maximal length of copolymer obtained depends on the degree of steric congestion a to the amide. Moreover, the presence of an aromatic ring in the amide substituent (1d′ or 1e′) significantly reduced propagation efficiency.

Given the unique polymer backbone generated in the i-AROMP reaction, the thermostability of poly(1c′-alt-3)_(n) was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) in air. The T_(g) of poly(1c′-alt-3)₉₇ is 86° C.±0.7° C. and it has a T_(d10)=130° C. (5 wt %). Decomposition of poly(1c′-alt-3)₄₂₄ occurred before the glass transition could be achieved. The high T_(g) of poly(1c′-alt-3)₉₇ can be ascribed to its relatively rigid backbone, the large size of the amide substituents, and expected strength of the intermolecular interactions.

Conclusions.

Bicyclo[4.2.0]oct-7-ene-7-carboxamides of primary amines are quantitatively isomerized to bicyclo[4.2.0]oct-1(8)-ene-8-carboxamides in the presence of catalyst 2. Moreover, reaction of compound 1d to give 1d′, which is complete within 15 minutes, is by far the fastest ruthenium-catalyzed olefin isomerization reported to date. This isomerization of an internal olefin in a bicyclic system provides a facile approach to synthesize tetra-substituted bicyclo[4.2.0]oct-1(8)-ene-8-carboxamides.

Remarkably, bicyclic tetra-substituted α, β-unsaturated amides are excellent AROMP substrates for the preparation of long, alternating copolymers. Isomerized unsaturated amides 1a′, 1b′, 1c′ and 1d′ undergo alternating ROMP with cyclohexene 1.5-4 times more rapidly than previously studied 1-cyclobutenecarboxylic acid esters or bicyclo[4.2.0]oct-7-ene-7-carboxylic esters. The isomerized amide AROMP reaction is compatible with a variety of amides that provide functional group handles. This facile sequence, isomerization followed by alternating ring-opening cross metathesis of A and ring-opening cross metathesis of B, provides an efficient entry to well-controlled architectures, enables the production of linear, soluble, and impressively long (greater than 100 and up to 400 AB units) alternating polymers with superior monomer economics, and unlocks the prospect of employing functionalized alternating and sequence-specific copolymers in multiple applications.

General Information

General Procedure for NMR Scale Isomerization Reactions. Under an N₂ atmosphere, a solution of the original amide and catalyst 2 was prepared in the indicated solvent (600 μL) in an NMR tube and NMR spectra were acquired at 35° C. At the end of the isomerization reaction (after complete consumption or no further isomerization of amide as judged by the change of the olefinic proton resonance), each reaction was terminated with ethyl vinyl ether (100 μL) and stirred for 30 min. The solvent was evaporated and the resulting residue was purified by silica chromatography to isolate the isomerized amide.

i-[4.2.0] Amide 1a′. Amide 1a (28 mg, 120 20 equiv) and catalyst 2 (5.3 mg, 6 μmol, 1 equiv) were mixed in CD₂Cl₂ in an NMR tube for 16 h; during this time, the integral for the olefinic proton decreased to 10% of its original value. The mixture was concentrated and the product was isolated by chromatography (100:1/CH₂Cl₂:MeOH) to yield 24 mg (80%) of 1a′. ¹H NMR (500 MHz, CDCl₃): δ 5.99 (s, 1H, CONH), 4.68 (m, 1H, CH), 3.78 (s, 3H, OCH₃), 2.88 (dd, J=12.2, 6.7 Hz, 1H, CH₂), 2.73 (ddd, J=15.4, 7.6, 3.9 Hz, 1H, CH₂), 2.38 (m, 1H, CH), 2.24 (m, 1H, CH₂), 2.10 (m, 2H, CH₂), 1.94 (m, 1H, CH₂), 1.75 (m, 1H, CH₂), 1.45 (dt, J=18.6, 9.3 Hz, 3H, CH₃), 1.34 (m, 2H, CH₂), 1.16 (m, 1H, CH₂).

i-[4.2.0] Amide 1b′. Amide 1b (67 mg, 300 μmol, 50 equiv) and catalyst 2 (5.3 mg, 6 μmol, 1 equiv) were mixed in CD₂CL₂ in an NMR tube for 8 h. ¹H NMR of the crude 1b′ (500 MHz, CDCl₃): δ 5.98 (s, 0.9H, CONH), 4.11 (d, J=5.3 Hz, 2H, side chain CH₂), 3.78 (s, 3H, OCH₃), 2.87 (dd, J=13.4, 2.7 Hz, 1H, CH₂), 2.75 (dt, J=12.0, 3.8 Hz, 1H, CH₂), 2.37 (m, 1H, CH), 2.23 (m, 1H, CH₂), 2.10 (m, 2H, CH₂), 1.93 (m, 1H, CH₂), 1.75 (m, 1H, CH₂), 1.34 (m, 2H, CH₂), 1.12 (m, 1H, CH₂).

i-[4.2.0] Amide 1c′. Amide 1c (58 mg, 300 μmol, 50 equiv) and catalyst 2 (5.3 mg, 6 μmol, 1 equiv) were mixed in CD₂Cl₂ in an NMR tube for 1.5 h, when isomerization was complete. The mixture was concentrated and the product was isolated by chromatography (100:1/CH₂Cl₂:MeOH) to yield 49 mg (85%) of 1c′. ¹H NMR (500 MHz, CDCl₃): δ 5.50 (s, 1H, CONH), 3.21 (m, 2H, side chain CH₂), 2.81 (dd, J=13.4, 2.7 Hz, 1 Hz, CH₂), 2.65 (dt, J=12.0, 3.8 Hz, 1H, CH₂), 2.31 (m, 1H, CH), 2.15 (m, 1H, CH₂), 2.04 (m, 2H, CH₂), 1.89 (m, 1H, CH₂), 1.69 (m, 2H, side chain CH₂), 1.51 (m, 2H, CH₂), 1.27 (m, 2H, CH₂), 0.91 (t, J=7.5 Hz, 3H, CH₃). ¹³C NMR (126 MHz, CD₂Cl₂): δ 164.1 (CONH), 161.7 (═C), 126.7 (═CCONH), 40.4 (side chain CH₂), 37.6 (CH), 33.9 (CH₂), 32.8 (CH₂), 27.1 (CH₂), 26.6 (CH₂), 24.5 (CH₂), 22.9 (side chain CH₂), 11.3 (CH₃). HRMS (ESI) calcd. for C₁₂H₁₉NO [M+H]⁺194.1539, found 194.1535. λ_(max) 224 nm was consistent with the λ_(max) 223 nm previously reported for bicyclo[4,2,0]oct-1(8)-ene-8-carboxyamide. Fleming, Ian; Harley-Mason, John. Journal of the Chemical Society (1964), (June), 2165-74.

i-[4.2.0] Amide 1c′ with MeOH. A 0.01 M fresh solution of catalyst 2 in 600 μL CD₂Cl₂ was divided into two NMR tubes, a 50 μL aliquot of MeOH (in large excess relative to catalyst 2) was added to one tube, and a 50 μL aliquot of CD₂Cl₂ was added to the second tube, both tubes were stirred for 2 h. Monomer 1c (10 equiv in 250 μL CD₂Cl₂) was added to each tube, and the kinetics of isomerization were monitored by ¹H NMR spectroscopy.

i-[4.2.0] Amide 1d′. Amide 1d (23 mg, 120 μmol) and catalyst 2 (5.3 mg, 6 μmol) were mixed in CD₂Cl₂ in an NMR tube; after 20 min, isomerization was complete. The mixture was concentrated and the product was isolated by chromatography (100:1/CH₂Cl₂:MeOH) to yield 17.5 mg (78%) of 1d′. ¹H NMR (500 MHz, CD₂Cl₂): δ 7.61 (d, J=7.8 Hz, 2H, Ph), 7.37 (t, J=7.6 Hz, 2H, Ph), 7.20 (s, 1H, CONH), 7.13 (t, J=7.4 Hz, 1H, Ph), 2.98 (dd, J=13.4, 2.7 Hz, 1Hz, CH₂), 2.84 (dt, J=12.0, 3.8 Hz, 1H, CH₂), 2.49 (m, 1H, CH₂), 2.35 (m, 1H, CH₂), 2.20 (m, 2H, CH₂), 2.00 (m, 1H, CH₂), 1.81 (m, 1H, CH₂), 1.44 (m, 2H, CH₂), 1.21 (m, 1H, CH₂).

i-[4.2.0] Amide 1e′. Amide 1e (68 mg, 300 μmol, 50 equiv) and catalyst 2 (5.3 mg, 6 μmol, 1 equiv) were mixed in CD₂Cl₂ in an NMR tube for 6 h when isomerization was complete. ¹H NMR of the crude product 1e′ (600 MHz, CD₂Cl₂): δ 7.20 7.02 (m, 4H, Ph), 5.64 (s, 1H, CONH), 3.3 (m, 2H, side chain CH₂), 2.85 (m, 1H, CH₂), 2.63 (m, 3H, ring CH₂ and side chain CH₂), 2.33 (m, 4H, ring CH and side chain CH₂), 2.13 (m, 2H, side chain CH₂), 2.03 (m, 1H, CH₂), 1.93 (m, 1H, CH₂), 1.84 (m, 2H, CH₂), 1.76 (m, 1H, CH₂), 1.32 (m, 2H, CH₂), 1.11 (m, 1H, CH₂).

i-[4.2.0] Amide 1e′ Monitored with ¹³C NMR Spectroscopy. Amide 1e (19.2 mg, 67 μmol, 1 equiv) and catalyst 2 (60 mg, 67 μmol, 1 equiv) were mixed in CD₂Cl₂ in an NMR tube and the reaction was monitored with ¹³C NMR spectroscopy at 35° C.

i-[4.2.0] Amide 1e′ with 3-bromopyridine. A 0.01 M solution of catalyst 2 in CD₂Cl₂ was divided into two NMR tubes, 3-bromopyridine (50 equiv) was added to one tube. Monomer 1e (10 equiv) was added to both aliquots ([2]_(final)=0.005 M), and the extent of isomerization was evaluated by ¹H NMR spectroscopy over 14 h.

i-[4.2.0] Amide 1e′ with Cl₂(H₂IMes)(PCy₃)Ru═CHPh. A 0.1 M solution of monomer 1e was divided into two NMR tubes. Catalyst Cl₂(H₂IMes)(PCy₃)Ru═CHPh in CD₂Cl₂ was added to one tube ([catalyst]_(final)=0.01 M, [1e′]_(final)=0.05 M) and 2 in CD₂Cl₂ was added to the second tube ([2]_(final)=0.01 M), and the kinetics of isomerization were monitored by ¹H NMR spectroscopy.

i-[4.2.0] Amide 1e′ with 1,4-benzoquinone. A 0.01 M solution of catalyst 2 in CD₂Cl₂ was divided into two NMR tubes, 1,4-benzoquinone (5 equiv relative to 2) was added to one tube. Monomer 1e (10 equiv) was added to both tubes ([2]_(final)=0.005 M) and the extent of isomerization was evaluated by ¹H NMR spectroscopy over 14 h.

i-[4.2.0] Amide 1f′. Amide 1f or 1f* (16 mg, 60 μmol, 10 equiv) and catalyst 2 (5.3 mg, 6 μmol, 1 equiv) were mixed in CDCl₃ in an NMR tube for 24 h, at which point the integral for the olefinic proton had decreased to 30% or 10% of its original value, respectively. Partial ¹H NMR spectroscopy of the crude 1f′ (600 MHz, CD₂Cl₂): δ 6.69 (s, 0.1H, ═CH), 6.31 (m, 0.1H, CONH), 6.09 (d, J=6.9 Hz, 0.9H, CONH). Partial ¹H NMR of the crude 1f*′ (600 MHz, CD₂Cl₂): δ 6.71 (s, 0.2H, ═CH), 6.36 -6.26 (m, 0.3H, CONH), 6.11 (d, J=6.9 Hz, 0.7H, CONH). (Partial ¹H NMR spectroscopic data are reported due to incomplete isomerization and significant upfield overlap of 1f/1f* with the new peaks from 1f′/1f*′.)

Attempted Isomerization of Amide 4. Amide 4 (27 mg, 120 μmol, 20 equiv) and catalyst 2 (5.3 mg, 6 μmol) were mixed in CD₂Cl₂ in an NMR tube for 18 h. Only a 2% of decrease in the intensity of the olefinic resonance of amide 4 was observed.

General Procedure for NMR Scale AROMP Reactions. All kinetic experiments were performed at least twice, and preparative polymerization experiments were performed three times. Under an N₂ atmosphere, a solution of amide 1 in CD₂Cl₂ (300 μL) was added to the NMR tube. Then 300 μL of catalyst 2 solution was added to the NMR tube. After complete mixing of the solution, NMR spectra were acquired at 35° C. Cyclohexene 3 was added after the amide was completely converted to its tetrasubstituted isomer as judged by the disappearance of the olefinic proton resonance around 6.7 ppm. This procedure was used for the preparation of polymers with up to 50 AB repeats. To ensure narrow dispersities, in the preparation of longer alternating polymers, the isomer 1′ was isolated and mixed with fresh catalyst 2 in CD₂Cl₂. Cyclohexene 3 was added after catalyst 2 completely initiated as determined by the disappearance of the Ru alkylidene resonance at 19.1 ppm in the ¹H NMR spectrum. When the propagation stopped or the isomerized amide disappeared as judged by a complete upfield shift of the amide N—H resonance from ˜5.4 ppm to ˜6 ppm, the reaction was quenched with ethyl vinyl ether and stirred for 30 min. The solvent was evaporated, and alternating copolymer was purified by step chromatography (100% CH₂Cl₂ to remove contaminants, then 20:1/CH₂Cl₂:MeOH to elute copolymer). The theoretical Mntheor was calculated from the monomer:catalyst feed ratio.

poly(1a′-alt-3)₅₀. Amide 1a′ (14.2 mg, 60 μmol, 50 equiv), catalyst 2 (1.1 mg, 1.20 μmol, 1 equiv) and 3 (9.8 mg, 120 μmol, 100 equiv) were mixed in CDCl₃ in an NMR tube. After 2 h, amide 1a′ was completely consumed. Flash column chromatography of the crude product yielded poly(1a′-alt-3)₅₀ (14.9 mg, 78% yield). ¹H NMR (700 MHz, CDCl₃): δ 7.45-7.27 (m, 5H, Ph), 6.45-6.08 (m, 77H, ═CH and CONH), 5.08 (m, 45H, ═CH), 4.63 (m, 45H, CH), 3.77 (m, 142H, CH₃), 2.55 (m, 45H), 2.41 (m, 45H), 2.16-1.95 (m, 320H), 1.64-1.50 (m, 157H), 1.43-1.28 (m, 530H). M_(n) ^(theor)=15 800. M_(n) ^(GPC)=12 500. M_(w) ^(GPC)=15 100.

_(M)=1.2.

poly(1a′-alt-3)₁₀₀. Amide 1a′ (28.5 mg, 120 μmol, 100 equiv), catalyst 2 (1.1 mg, 1.20 μmol, 1 equiv) and 3 (19.6 mg, 240 μmol, 200 equiv) were mixed in CDCl₃ in an NMR tube. After 6 h, amide 1a′ was completely consumed. Flash column chromatography of the crude product yielded poly(1a'-alt-3)₁₀₀ (26.8 mg, 70% yield). ¹H NMR (700 MHz, CD₂Cl₂): δ 7.45-7.27 (m, 5H, Ph), 6.50-6.10 (m, 188H, ═CH and CONH), 5.08 (m, 105H, ═CH), 4.63 (m, 98H, CH), 3.77 (m, 296H, CH₃), 2.55 (m, 104H), 2.38 (m, 105H), 2.16-1.95 (m, 730H), 1.64-1.28 (m, 1560H). ¹³C NMR (126 MHz, CD₂Cl₂): δ 173.6, 169.2, 141.6, 136.0, 135.8, 120.8, 52.2, 48.1, 43.7, 43.5, 33.1, 30.0, 28.8, 28.4, 28.1, 26.9, 26.5, 23.6, 18.2. M_(n) ^(theor)=31 900. M_(n) ^(GPC)=29 100. M_(w) ^(GPC)=30 700.

_(M)=1.1.

poly(1b′-alt-3)₁₄₀. Amide 1b′ (40.2 mg, 180 μmol, 150 equiv), catalyst 2 (1.1 mg, 1.20 μmol, 1 equiv) and 3 (29.4 mg, 360 μmol, 300 equiv) were mixed in CDCl₃ in an NMR tube. After 2.5 h, amide 1b′ was completely consumed. Flash column chromatography of the crude product yielded poly(1b′-alt-3)₁₄₀ (34.0 mg, 62% yield). ¹H NMR (700 MHz, CD₂Cl₂): δ 7.45-7.27 (m, 5H, Ph), 6.64-6.42 (m, 133H, CONH), 6.27 (m, 141H, ═CH), 5.10 (m, 146H, ═CH), 4.02 (m, 370H, CH₂), 3.76 (m, 420H, CH₃), 2.58 (m, 160H), 2.41 (m, 118H), 2.23-2.01 (m, 1020H), 1.64-1.57 (m, 334H), 1.44-1.30 (m, 1288H). M_(n) ^(theor)=45 700. M_(n) ^(GPC)=34 000. M_(w) ^(GPC)=40 300.

_(M)=1.2.

poly(1b′-alt-3)₂₆₀. Amide 1b′ (40.2 mg, 180 μmol, 300 equiv), catalyst 2 (0.55 mg, 0.60 μmol, 1 equiv) and 3 (29.4 mg, 360 μmol, 600 equiv) were mixed in CDCl₃ in an NMR tube. After 3.5 h, 90% of amide 1b′ was consumed. Flash column chromatography of the crude product yielded poly(1b′-alt-3)₂₆₀ (27.5 mg, 52% yield). ¹H NMR (700 MHz, CD₂Cl₂): δ 7.45-7.27 (m, 5H, Ph), 6.63-6.41 (m, 242H, CONH), 6.27 (m, 256H, ═CH), 5.10 (m, 267H, ═CH), 4.02 (m, 510H, CH₂), 3.76 (m, 769H, CH₃), 2.58 (m, 284H), 2.41 (m, 206H), 2.23-2.01 (m, 2036H), 1.68-1.57 (m, 633H), 1.44-1.30 (m, 2358H). ¹³C NMR (126 MHz, CD₂Cl₂): δ 170.6, 169.7, 141.6, 136.3, 135.7, 121.0, 60.1, 52.1, 43.4, 41.2, 33.3, 30.0, 28.7, 28.3, 27.9, 26.8, 24.0, 20.6, 14.2. M_(n) ^(theor)=91 000. M_(n) ^(GPC)=69 600. M_(w) ^(GPC)=80 900.

_(M)=1.2.

poly(1c′-alt-3)₁₀. Amide 1c (11.6 mg, 60 μmol, 10 equiv) and catalyst 2 (5.3 mg, 6 μmol, 1 equiv) were mixed. Upon completion of isomerization, 3 (9.8 mg, 120 μmol, 20 equiv) was added and after 1.5 h, amide 1c′ was completely consumed. Flash column chromatography of the crude product yielded poly(1c′-alt-3)₁₀ (12 mg, 72% yield). ¹H NMR (500 MHz, CD₂Cl₂): δ 7.45-7.21 (m, 5H, Ph), 6.40-5.57 (m, 20H, ═CH and CONH), 5.09 (m, 10H, ═CH), 3.31-3.16 (m, 26H, CH₂), 2.68-1.09 (m, 342H), 0.95 (t, J=7.4 Hz, 38H, CH₃).

poly(1c′-alt-3)₅₀. Amide 1c (11.6 mg, 60 μmol, 50 equiv) and catalyst 2 (1.1 mg, 1.20 μmol, 1 equiv) were mixed in CD₂Cl₂ in an NMR tube. Upon completion of isomerization, 3 (9.8 mg, 120 μmol, 100 equiv) was added and after 2 h, amide 1c′ was completely consumed. Flash column chromatography of the crude product yielded poly(1c′-alt-3)₅₀ (14 mg, 74% yield). ¹H NMR (500 MHz, CD₂Cl₂): δ 7.45-7.27 (m, 5H, Ph), 6.40-5.57 (m, 97H, ═CH and CONH), 5.09 (m, 49H), 3.24 (m, 105H, CH₂), 2.58 (m, 46H), 2.39 (m, 44H), 2.29-1.90 (m, 363H), 1.80-1.17 (m, 700H), 1.04-0.87 (m, 160H, CH₃). M_(n) ^(theor)=14 500. M_(n) ^(GPC)=9 400. M_(w) ^(GPC)=17 000.

_(M)=1.8.

poly(1c′-alt-3)₁₀₀. Amide 1c′ (23.2 mg, 120 μmol, 100 equiv), catalyst 2 (1.1 mg, 1.20 μmol, 1 equiv) and 3 (19.6 mg, 240 μmol, 200 equiv) were mixed in CD₂Cl₂ in an NMR tube. After 2 h, amide 1c′ was completely consumed. Flash column chromatography of the crude product yielded poly(1c′-alt-3)₁₀₀ (24 mg, 85% yield). ¹H NMR (500 MHz, CD₂Cl₂): δ 7.45-7.27 (m, 5H, Ph), 6.40-5.57 (m, 186H, ═CH and CONH), 5.09 (m, 98H, ═CH), 3.24 (m, 199H, CH₂), 2.58 (m, 98H), 2.39 (m, 84H), 2.29-1.90 (m, 697H), 1.75-1.17 (m, 1259H), 1.04-0.87 (m, 311H). M_(n) ^(theor)=28 100. M_(n) ^(GPC)=20 500. M_(w) ^(GPC)=28 400.

_(M)=1.4.

poly(1c′-alt-3)₄₂₀. Amide 1c′ (23.2 mg, 120 μmol, 500 equiv), catalyst 2 (0.22 mg, 0.24 μmol, 1 equiv) and 3 (19.6 mg, 240 μmol, 1000 equiv) were mixed in CD₂Cl₂ in an NMR tube. After 6 h, amide 1c′ was completely consumed. Flash column chromatography of the crude product yielded poly(1c′-alt-3)₄₂₀ (13 mg, 46% yield). ¹H NMR (500 MHz, CD₂Cl₂): δ 7.36 (m, 5H, Ph), 6.44-5.65 (m, 741H, ═CH and CONH), 5.22-4.99 (m, 424H, ═CH), 3.33-3.13 (m, 871H, CH₂), 2.55 (m, 447H), 2.48-2.33 (m, 390H), 2.33-1.87 (m, 3115H), 1.80-1.15 (m, 6126H), 1.06-0.82 (m, 1522H). ¹³C NMR (126 MHz, CD₂Cl₂): δ 169.8, 141.8, 136.9, 134.4, 120.8, 43.7, 41.3, 33.1, 30.0, 30.0, 28.8, 28.3, 28.1, 26.9, 23.0, 11.3. M_(n) ^(theor)=137 700. M_(n) ^(GPC)=111 600. M_(w) ^(GPC)=130 900.

_(M)=1.2.

poly(1d′-alt-3-D₁₀)₁₀. Amide 1d (13.7 mg, 60 μmol, 10 equiv) and catalyst 2 (5.3 mg, 6.0 μmol, 1 equiv) were mixed in CD₂Cl₂ in an NMR tube. Monomer 3-D₁₀ (9.8 mg, 120 μmol, 20 equiv) was added upon completion of isomerization. And after 1 h, amide 1d′ was completely consumed. Flash column chromatography of the crude product yielded poly(1d′-alt-3-D₁₀)₁₀ (13 mg, 68% yield). ¹H NMR (500 MHz, CD₂Cl₂): δ 7.89 (s, 10H, CONH), 7.59 (m, 20H, Ph), 7.38-7.26 (m, 20H, Ph), 7.10 (m, 10H, Ph), 3.67 (m, 10H), 2.63 (m, 10H), 2.4 (m, 20H), 2.15 (m, 20H), 2.08 (m, 10H), 1.67-1.23 (m, 203H).

poly(1d′-alt-3)₅₀. Amide 1d (13.7 mg, 60 μmol, 50 equiv) and catalyst 2 (1.1 mg, 1.20 μmol, 1 equiv) were mixed in CD₂Cl₂ in an NMR tube. Monomer 3 (9.8 mg, 120 μmol 100 equiv) was added upon completion of isomerization. And after 1 h, amide 1d′ was completely consumed. Flash column chromatography of the crude product yielded poly(1d′-alt-3)₅₀ (14 mg, 76% yield). ¹H NMR (500 MHz, CD₂Cl₂): δ 7.89 (s, 43H, CONH), 7.59 (m, 118H, Ph), 7.38-7.26 (m, 143H, Ph), 7.10 (m, 65H, Ph), 6.30 (m, 46H, ═CH), 5.11 (m, 50H, ═CH), 3.67 (m, 39H), 2.77 1.23 (m, 1359H). ¹³C NMR (126 MHz, CD₂Cl₂): δ 168.7, 142.1, 139.2, 137.7, 136.6, 68.2, 44.3, 33.7, 30.5, 29.2, 28.9, 28.5, 27.4, 27.0, 26.1, 24.1.M_(n) ^(theor)=15 600. M_(n) ^(GPC)=10 100. M_(w) ^(GPC)=16 000.

_(M)=1.6.

General Procedures for the Synthesis of Bicyclo[n.2.0]Acids.

The methyl bicyclic cyclobutenecarboxylate, [n.2.0] ester was obtained according to the literature Snider B B, Rodini D J, Cionn R S E, & Sealfon S J. Am. Chem. Soc. 1979, 101:5283-5493; Tan L, Parker K A, & Sampson N S Macromolecules 2014, 47:6572-6579. Then [n.2.0] ester in THF was cooled in an ice bath, 2N KOH was added, and the solution was stirred for 30 min. The ice bath was removed and the reaction mixture was allowed to warm to 25° C. and stirred for another 4 h. THF was evaporated and the aqueous solution was acidified with 2N HCl to pH 2. The solution was extracted with CH₂Cl₂ (3×20 mL) and the combined CH₂Cl₂ solution was dried over anhydrous MgSO₄. The solvent was removed after filtration and the product was used without further purification.

[4.2.0] Acid 5. The methyl bicyclo[4.2.0]oct-7-ene-7-carboxylate (2.00 g, 12.0 mmol) in THF (5 mL) was hydrolyzed in the presence of 2N KOH (20 mL), and the product bicyclo[4.2.0]oct-7-ene-7-carboxylic acid 5 (1.74 g, 95%) was used without further purification.

[3.2.0] Acid 6. The methyl bicyclo[3.2.0]hepta-6-ene-6-carboxylate (500 mg, 3.29 mmol) was hydrolyzed by the procedure described above to yield acid 6 (350 mg, 80%). It was converted to the desired amide without further purification.

General Procedure for the Synthesis of Bicyclo[n.2.0]Alkene Amides.

Bicyclo[n.2.0]alkene carboxylic acid (n=3 or 4), ethyl, dimethylaminopropyl carbodiimide hydrochloride (EDC.HCl), and the desired amine were dissolved in dry CH₂Cl₂ in a 50-mL flask. The solution was cooled in an ice bath and DIPEA was added. The mixture was stirred for 8 h at 25° C. until the acid was consumed. The reaction mixture was washed sequentially with 5% NaHCO₃ (3×), 1N HCl (3×) and brine (2×) and dried over anhydrous MgSO₄. The solvent was filtered and removed by evaporation. The crude product was subjected to silica flash chromatography.

[4.2.0] Amide 1a. Acid 5 (100 mg, 0.66 mmol), L-Ala-OMe.HCl (104 mg, 0.72 mmol), EDC.HCl (139 mg, 0.72 mmol) and DIPEA (370 μL, 2.1 mmol) were allowed to react in 20 mL CH₂Cl₂ and subjected to work up as described. Chromatography (97:3/CH₂Cl₂:MeOH) yielded amide 1a as a mixture of diastereomers (146 mg, 80%). ¹H NMR (600 MHz, CDCl₃): δ 6.70 (d, J=6.7 Hz, 1H, ═CH), 6.19 (d, J=5.6 Hz, 1H, CONH), 4.61 (qd, J=7.2, 2.6 Hz, 1H, side chain CH), 3.71 (s, 3H, OCH₃), 3.05 (m, 1H, CH), 2.74 (m, 1H, CH), 1.79 (m, 1H, CH₂), 1.69 (m, 2H, CH₂), 1.52 (m, 3H, CH₂), 1.39 (m, 5H, CH₂ and CH₃). ¹³C NMR (126 MHz, CDCl₃): δ 173.5 (COOR), 162.1 (CONH), 145.2 (═CH), 144.1 (═CH), 52.4 (OCH₃), 47.5 (side chain CH), 39.3 (CH), 37.6 (CH), 23.8 (CH₂), 23.6 (CH₂), 18.7 (CH₂), 18.5 (CH₂), 18.2 (CH₃). Apparent peak doublets that arise from the presence of two diastereomers were reported as a single chemical shift. HRMS (ESI) calcd. for C₁₃H₁₉NO₃ [M+H]⁺238.1438, found 238.1429.

[4.2.0] Amide 1b. Acid 5 (100 mg, 0.66 mmol), Gly-OMe.HCl (87 mg, 0.69 mmol), EDC.HCl (139 mg, 0.72 mmol) and DIPEA (570 μL, 3.3 mmol) were allowed to react in 20 mL CH₂Cl₂ and subjected to work up as described. Chromatography (97:3/CH₂Cl₂:MeOH) yielded amide 1b, (146 mg, 80%). ¹H NMR (400 MHz, CDCl₃): δ 6.71 (s, 1H, ═CH), 6.36 (s, 1H, CONH), 4.03 (m, 2H, side chain CH₂), 3.70 (s, 3H, OCH₃), 3.02 (dd, J=10.4, 5.3 Hz, 1H, CH), 2.74 (dd, J=9.7, 4.8 Hz, 1H, CH), 1.77 (m, 1H, CH₂), 1.67 (m, 2H, CH₂), 1.52 (m, 3H, CH₂), 1.37 (m, 2H, CH₂). ¹³C NMR (101 MHz, CDCl₃): δ 170.3 (COOR), 162.6 (CONH), 145.1 (═CH), 143.9 (═CH), 52.1 (OCH₃), 40.5 (side chain CH₂), 39.3 (CH), 37.6 (CH), 23.6 (CH₂), 23.5 (CH₂), 18.5 (CH₂), 18.1 (CH₂). HRMS (ESI) calcd. for C₁₂H₁₇NO₃ [M+H]⁺224.1281, found 224.1273.

[4.2.0] Amide 1c. Acid 5 (300 mg, 2.0 mmol), propyl amine (130 mg, 2.2 mmol), EDC.HCl (421 mg, 2.2 mmol) and DIPEA (767 μL, 4.4 mmol) were allowed to react in 60 mL CH₂Cl₂ and subjected to work up as described. Chromatography (97:3/CH₂Cl₂:MeOH) yielded amide 1c, (307 mg, 80%). ¹H NMR (400 MHz, CDCl₃): δ 6.69 (d, J=0.9 Hz, 1H, ═CH), 5.77 (s, 1H, CONH), 3.25 (qd, J=13.3, 6.3 Hz, 2H, CH₂), 3.02 (dd, J=10.4, 5.6 Hz, 1H, CH), 2.76 (q, J=4.9 Hz, 1H, CH), 1.82 (m, 1H, CH₂), 1.70 (m, 2H, CH₂), 1.54 (m, 5H, side chain CH₂ and ring CH₂), 1.42 (m, 2H, CH₂), 0.91 (t, J=7.4 Hz, 3H, CH₃). ¹³C NMR (101 MHz, CDCl₃): δ 162.9 (CONH), 144.6 (═CH), 144.0 (═CH), 40.6 (side chain CH₂), 39.3 (CH), 37.4 (CH), 23.9 (CH₂), 23.7 (CH₂), 22.8 (side chain CH₂), 18.7 (CH₂), 18.2 (CH₂), 11.2(CH₃). HRMS (ESI) calcd. for C₁₂H₁₉NO [M+H]⁺194.1539, found 194.1532.

[4.2.0] Amide 1d. Acid 5 (300 mg, 2.0 mmol), aniline (204 mg, 2.2 mmol), EDC.HCl (421 mg, 2.2 mmol) and DIPEA (767 μL, 4.4 mmol) were allowed to react in 60 mL CH₂Cl₂ and subjected to work up as described. Chromatography (98:2/CH₂Cl₂:MeOH) yielded amide 1d, (170 mg, 40%) free of the major impurity N-phenyl-8-(phenylamino)-bicyclo[4.2.0]octane-7-carboxamide. ¹H NMR (500 MHz, CDCl₃): δ 7.58 (d, J=7.8 Hz, 2H, Ph), 7.36 (s, 1H, CONH), 7.31 (t, J=7.9 Hz, 2H, Ph), 7.10 (t, J=7.4 Hz, 1H, Ph), 6.83 (s, 1H, ═CH), 3.15 (dd, J=10.5, 5.5 Hz, 1H, CH), 2.82 (q, J=5.1 Hz, 1H, CH), 1.89 (m, 1H), 1.78 (m, 2H), 1.60 (m, 3H), 1.46 (m, 2H). ¹³C NMR (126 MHz, CDCl₃): δ 160.6 (CONH), 145.4 (═CH), 145.0 (═CH), 137.6 (Ph), 129.0 (Ph), 129.0 (Ph), 124.2 (Ph), 124.2 (Ph), 119.6 (Ph), 39.6 (CH), 37.6 (CH), 24.0 (CH₂), 23.7 (CH₂), 18.8 (CH₂), 18.3 (CH₂). HRMS (ESI) calcd. for C₁₅H₁₇NO [M+H]⁺228.1383, found 228.1382.

[4.2.0] Amide 1e. Acid 5 (97 mg, 0.64 mmol), 3-p-tolyl-propan-1-amine (100 mg, 0.67 mmol), EDC.HCl (129 mg, 0.67 mmol) and DIPEA (226 μmol, 1.3 mmol) were allowed to react in 20 mL CH₂Cl₂ and subjected to work up as described. Chromatography (97:3/CH₂Cl₂:MeOH) yielded amide 1e, (147 mg, 85%). ¹H NMR (600 MHz, CDCl₃): δ 7.17 6.97 (m, 4H, Ph), 6.65 (s, 1H, ═CH), 5.66 (m, 1H, CONH), 3.35 (m, 2H, side chain CH₂), 2.97 (dd, J=10.5, 5.6 Hz, 1H, CH), 2.75 (q, J=5.1 Hz, 1H, CH), 2.62 (t, J=7.6 Hz, 2H, side chain CH₂), 2.30 (s, 3H, CH₃), 1.84 (m, 2H, side chain CH₂), 1.78 (m, 2H, CH₂), 1.65 (m, 1H, CH₂), 1.55 (m, 3H, CH₂), 1.42 (m, 2H, CH₂). ¹³C NMR (101 MHz, CDCl₃): δ 162.7 (CONH), 144.7 (═CH), 143.7 (═CH), 138.3 (Ph), 135.3 (Ph), 129.0 (Ph), 129.0 (Ph), 128.1 (Ph), 128.1 (Ph), 39.2 (side chain CH₂), 38.6 (CH), 37.4 (CH), 32.9 (side chain CH₂), 31.2 (side chain CH₂), 23.9 (CH₂), 23.7 (CH₂), 20.8 (side chain CH₃), 18.6 (CH₂), 18.2 (CH₂). HRMS (ESI) calcd. for C₁₉H₂₅NO [M+H]⁺284.2009, found 284.2005.

[4.2.0] Amide 1f. Acid 5 (200 mg, 2.0 mmol), (S)-2-phenylglycinol (400 mg, 2.2 mmol), EDC.HCl (281 mg, 2.2 mmol) and DIPEA (767 4.4 mmol) were allowed to react in 40 mL CH₂Cl₂ and subjected to work up as described. The crude product was developed on silica TLC plates with 20:1/CH₂Cl₂:MeOH and two partially separated spots were observed with R_(f) values=0.32 and 0.25. Chromatography (97:3/CH₂Cl₂:MeOH) yielded two diastereomers: A (60 mg, 11%) and A* (50 mg, 9%). Each diastereomer (50 mg, 0.18 mmol) was mixed with acetic anhydride (20.7 mg, 0.203 mmol) and TEA (20.5 mg, 0.203 mmol) in anhydrous CH₂Cl₂, and the mixture was stirred for 16 h. After concentrating in vacuo, the reaction mixture was subjected to flash chromatography (97:3/CH₂Cl₂:MeOH) to yield amide if (41 mg, 62%) from the higher R_(f) alcohol A. ¹H NMR (500 MHz, CDCl₃): δ 7.42-7.23 (m, 5H, Ph), 6.75 (s, 1H, ═CH), 6.20 (d, J=7.8 Hz, 1H, CONH), 5.35 (td, J=7.8, 5.0 Hz, 1H, CH), 4.50 (dd, J=11.5, 7.7 Hz, 1H, CH₂O), 4.26 (dd, J=11.5, 4.6 Hz, 1H, OCH₂), 3.06 (q, J=5.5 Hz, 1H, CH), 2.78 (q, J=4.9 Hz, 1H, CH), 2.04 (s, 3H, CH₃), 1.83 (m, 1H, CH₂), 1.76-1.68 (m, 2H, CH₂), 1.58 (m, 3H, CH₂), 1.44 (m, 2H, CH₂). ¹³C NMR (126 MHz, CDCl₃): δ 171.2 (COOR), 162.2 (CONH), 145.1 (═CH), 144.3 (═CH), 138.2 (Ph), 128.7 (Ph), 128.7 (Ph), 127.9 (Ph), 126.6 (Ph), 126.6 (Ph), 65.8 (OCH₂), 52.1 (side chain CH), 39.4 (CH), 37.6 (CH), 23.8 (CH₂), 23.7 (CH₂), 20.7 (CH₃), 18.7 (CH₂), 18.3 (CH₂). HRMS (ESI) calcd. for C₂₀H₂₅NO₃ [M+H]⁺314.1751, found 314.1749. Amide 1f* (45 mg, 66%) was obtained from the lower R_(f) alcohol A*. ¹E NMR (500 MHz, CDCl₃): δ 7.42-7.23 (m, 5H, Ph), 6.76 (s, 1H, ═CH), 6.27 (d, J=7.2 Hz, 1H, CONH), 5.35 (td, J=7.8, 4.6 Hz, 1H, CH), 4.54 (dd, J=11.5, 7.7 Hz, 1H, CH₂O), 4.27 (dd, J=11.5, 4.5 Hz, 1H, OCH₂), 3.07 (dd, J=10.5, 5.6 Hz, 1H, CH), 2.81 (dd, J=9.9, 4.9 Hz, 1H, CH), 2.03 (s, 3H, CH₃), 1.87 (m, 1H, CH₂), 1.75 (m, 2H, CH₂), 1.59 (m, 3H, CH₂), 1.46 (m, 2H, CH₂). ¹³C NMR (126 MHz, CDCl₃): δ 171.5 (COOR), 162.2 (CONH), 144.8 (═CH), 144.4 (═CH), 138.3 (Ph), 128.8 (Ph), 128.8 (Ph), 127.9 (Ph), 126.5 (Ph), 126.5 (Ph), 66.1 (OCH₂), 52.3 (side chain CH), 39.4 (CH), 37.7 (CH), 24.0 (CH₂), 23.7 (CH₂), 20.8 (CH₃), 18.7 (CH₂), 18.3 (CH₂). HRMS (ESI) calcd. for C₂₀H₂₅NO₃ [M+H]⁺314.1751, found 314.1742.

[3.2.0] Amide 4. Acid 6 (138 mg, 1 mmol), L-Ala-OMe.HCl (157 mg, 1.1 mmol), EDC.HCl (210 mg, 1.1 mmol) and DIPEA (570 μL, 3.3 mmol) were allowed to react in 25 mL CH₂Cl₂ and subjected to work up as described. Chromatography (97:3/CH₂Cl₂:MeOH) yielded amide 4 as a mixture of diastereomers (157 mg, 75%). ¹H NMR (600 MHz, CDCl₃): δ 6.49 (d, J=5.0 Hz, 1H, ═CH), 6.21 (s, 1H, CONH), 4.64 (m, 1H, CH), 3.75 (s, 3H, OCH₃), 3.32 (s, 1H, CH), 3.02 (d, J=7.2 Hz, 1H, CH), 1.78-1.70 (m, 1H), 1.68-1.60 (m, 2H, CH₂), 1.57-1.54 (m, 1H, CH₂), 1.40 (d, J=7.1 Hz, 3H, CH₃), 1.30-1.23 (m, 2H, CH₂). ¹³C NMR (101 MHz, CDCl₃): δ 173.5 (COOR), 161.6 (CONH), 142.1 (═CH), 140.6 (═CH), 52.4 (OCH₃), 47.4 (side chain CH), 45.8 (CH), 43.9 (CH), 25.6 (CH₂), 25.4 (CH₃), 23.0 (CH₂), 23.1 (CH₂), 18.6 (CH₂), 18.6 (CH₂). Apparent peak doublets that arise from the presence of two diastereomers were reported as a single chemical shift. HRMS (ESI) calcd. for C₁₂H₁₇NO₃ [M+H]⁺224.1281, found 224.1278.

1e Isomerization Monitored by ¹³C NMR Spectroscopy. Amide 1e (19.2 mg, 67 μmol, 1 equiv) and catalyst 2 (60 mg, 67 μmol, 1 equiv) were mixed in CD₂Cl₂ in an NMR tube and the reaction was monitored with ¹³C NMR spectroscopy at 35° C. (FIG. 4). 

We claim:
 1. A process for producing an alternating AB copolymer comprising the repeating unit I,

comprising: (1) optionally isomerizing a cyclobutene of structure III in the presence of an olefin metathesis catalyst to form a cyclobutene III′:

(2) polymerization of the cyclobutene III′ with a cyclohexene II:

in the presence of an olefin metathesis catalyst; wherein R is selected from the group consisting of H, C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group; n is between 2 and 500; each substituent R¹ through R⁴ is independently selected from the group consisting of H, aldehyde, C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₃-C₆ cycloalkyl, aryl, heterocyclyl, C₁-C₂₀ alkoxy, C₁-C₂₀ acyloxy, C₂-C₂₀alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino, and halogen, and adjacent substitutions of R¹-R⁴ may be taken together to form a 5- to 7-membered ring which may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group; and wherein R⁵ and R⁶ are taken together to form a 5- or 6-membered ring, which may contain up to two heteroatoms in the ring selected from O or N, and which may be unsubstituted or substituted with up to four substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group.
 2. The process according to claim 1, wherein the alternating AB copolymer comprises the repeating unit Ia

wherein X is O or NH; and R^(a) is selected from the group consisting of H, C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, C₁-C₂₀ alkoxy, C₂-C₂₀alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀alkylamino, C₂-C₂₀alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group.
 3. The process according to claim 1, wherein R⁵ and R⁶ are taken together to form a cyclohexyl ring, which may be substituted.
 4. The process according to claim 1, wherein the alternating AB copolymer comprises the repeating unit Ib

wherein R^(b) is selected from the group consisting of H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group.
 5. The process according to claim 1, wherein the cyclohexene has the structure IIa:

wherein each substituent R² and R³ is independently selected from H, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, C₁-C₂₀alkoxy, C₂-C₂₀alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino or halogen, and may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, and a heterocyclic group, and alternatively R² and R³ are be taken together to form a 5- to 7-membered ring which may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group.
 6. The process according to claim 5, wherein the cyclohexene has the structure:


7. The process according to claim 1, wherein the cyclobutene has the structure IIIa or IIIa′, in which the cyclobutene of structure IIIa is isomerized to a cyclobutene of structure IIIa′

in the presence of an olefin metathesis catalyst, wherein X is selected from O, or NH, and R^(a) is selected from the group consisting of H, C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₂-C₂₀alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group.
 8. The process according claim 1, wherein the cyclobutene has the structure IIIb or IIIb′, in which the cyclobutene of structure IIIb is isomerized to a cyclobutene of structure IIIb′

in the presence of an olefin metathesis catalyst; wherein R^(b) is selected from the group consisting of H, C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₂-C₂₀alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀alkenylamino, C₃-C₈cycloalkylamino, heterocyclylamino, or arylamino and may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group.
 9. The process according to claim 1, wherein the cyclobutene has the structure IIIc or IIIc′, in which the cyclobutene of structure IIIc is isomerized to a cyclobutene of structure IIIc′

in the presence of an olefin metathesis catalyst; wherein R^(b) is selected from the group consisting of H, C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₃-C₈ cycloalkyl, heterocyclyl, aryl, aralkyl, C₁-C₂₀ alkoxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, or arylamino and may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group; m is an integer from 0 to 4, and each R⁸ is independently selected from the group consisting of aldehyde, C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₃-C₆ cycloalkyl, aryl, heterocyclyl, C₁-C₂₀ alkoxy, C₁-C₂₀ acyloxy, C₂-C₂₀ alkenyloxy, C₃-C₆ cycloalkyloxy, aryloxy, heterocyclyloxy, C₁-C₂₀ alkylamino, C₂-C₂₀ alkenylamino, C₃-C₈ cycloalkylamino, heterocyclylamino, arylamino, or halogen; and adjacent substitutions of R⁸ may be taken together to form a 5- to 7-membered ring which may be substituted with up to three substituents selected from halo, CN, NO₂, oxo, amino, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, aryl, or a heterocyclic group.
 10. The process according to claim 9 wherein the cyclohexene is selected from formula IIa and the cyclobutene of structure IIIc is selected from IIIc 1, IIIc2, III3,IIIc4, IIIc5, and IIIc6:


11. The process according to claim 7, wherein R⁵ and R⁶ are taken together to form a cyclohexyl ring, which may be optionally substituted.
 12. The process according to claim 2, wherein R⁵ and R⁶ are taken together to form a cyclohexyl ring, which may be substituted.
 13. The process according to claim 8, wherein R⁵ and R⁶ are taken together to form a cyclohexyl ring, which may be substituted. 